This application claims the benefit of Taiwan application Serial No. 91118946, filed Aug. 22, 2002.
1. Field of the Invention
The invention relates in general to a multi-resolution charge-coupled device (CCD) sensing device, and more particularly to a multi-resolution CCD sensing device applied to the CCD module and the Contact Image Sensor (CIS) module.
2. Description of the Related Art
Scanners have become widely used in recent years. The user is required to choose from scanning modes with different resolutions when scanning, in accordance with the properties of the document to be scanned. There are several conventional ways to set the resolution, which might be accomplished by using either software or hardware. Using hardware is usually faster and more direct.
The scanning procedures for the scanner with the CCD module are stated as follows. The carriage in the scanner has a light source, and after the light source produces light, it is reflected by the document being scanned, and the light is directed back to the carriage. The light signal is processed by optical components, such as mirrors and lenses, and is then received by the CCD module. The CCD module senses the magnitude of the light signal and then generates corresponding scanned image data.
Referring to FIG. 1, a CCD module using a conventional CCD sensing apparatus is shown. The CCD module includes a CCD sensing device 102, a control circuit 104, and an output capacitor C. The CCD sensing device 102 includes a photo sensor set 106, a shift gate 108, and a CCD shift register 110. The CCD sensing device 102, with a resolution of 1200 dpi (dot per inch), is used here as an example. If a CCD sensing device 102 is used to sense a document of 8 inches in width, then the photo sensor set 106 includes 1200xc3x978=9600 photo sensing components. FIG. 1 shows eight photo sensing components, D1xcx9cD8, that convert light signals into charge signals. The photo sensing components may be photo diodes. The shift gate 108 is used for controlling the transmission of the charge signals. When the photo-sensing components are exposed to light for a predetermined period of time, the photo sensing components generate a corresponding amount of charge, and then the shift gate 108 is turned on to transfer the charge signals to the CCD shift register 110. The CCD shift register 110 may be a two-phase CCD shift register 110. The CCD shift register 110, with 1200 dpi for sensing a document of 8 inches in width, includes 19200 CCD components. FIG. 1 shows 16 CCD components, E1xcx9cE8 and E1xe2x80x2xcx9cE8xe2x80x2, that correspond to the photo-sensing components D1xcx9cD8. The CCD components E1xcx9cE8 and E1xe2x80x2xcx9cE8xe2x80x2 are arranged alternately, and are also controlled by phase signals F1 and F2, respectively. Subsequently, by the control of phase signals F1 and F2, the charge signals stored in the CCD components are sequentially output. As shown in FIG. 1, eight photo-sensing components D1xcx9cD8 out of the 9600 photo sensing components generate charge signals S1xcx9cS8. The charge signals S1xcx9cS8 can be transferred to CCD components E1xcx9cE8. The control circuit 104 is used to store the charge signals, which are output from the CCD shift register 110, in the capacitor C sequentially to acquire the analog output signal Out. The output signal Out is processed by a next stage circuit (not shown), and the scanned image data are then obtained.
However, users need to be able to use different scanning modes with different resolutions. For example, a high-resolution scanning mode is required if the document to be scanned is a color image. If the document to be scanned is text, it simply requires a low-resolution scanning mode. In FIG. 1, due to the CCD sensing device 102 is a high-resolution sensing device, some properties of the CCD sensing device 102 have to be discarded during low-resolution scanning. Besides, scanning time may be wasted during low-resolution scanning.
FIG. 1 shows the CCD sensing device 102 configured for high resolution and being used for low-resolution 600 dpi scanning; the operation is described as follows: after the photo-sensing components D1xcx9cD8 are exposed to light, the charge signals S1xcx9cS8 are stored in the CCD components E1xcx9cE8. When the charge signals S1xcx9cS8 are output, a simpler method is to require the control circuit 104 to store 4800 sequential charge signals, such as S2, S4, S6, and S8, etc., in capacitor C in order to obtain the 600 dpi scanned image data. Another improved method is to require the control circuit 104 to store 9600 sequential charge signals grouping every two charge signals together, such as S1+S2, S3+S4, S5+S6, and S7+S8, etc., in capacitor C to obtain the corresponding analog voltage values, such as charge signals S1+S2, S3+S4, S5+S6, and S7+S8, etc., so as to obtain 600 dpi scanned image data. Although the scanned image data are of low resolution, the time it takes to shift out the electric charges stored in the CCD components to the capacitor C is still the same as before and does not decrease. Therefore, for the conventional CCD sensing device 102, scanning at a low resolution take the same amount of time as scanning at a high resolution.
The chips for CCD sensing at different resolutions have been widely used in the marketplace. To solve the above-mentioned problem, CCD modules with multiple CCD sensing devices of several different resolutions have also become available on the market.
Referring to FIG. 2, a conventional CCD module with multiple CCD sensing devices is shown. The CCD module with three CCD sensing devices is used as an example for further illustration. The CCD module has a CCD sensing device 202a with a resolution of 1200 dpi, a CCD sensing device 202b with a resolution of 600 dpi, and a CCD sensing device 202c with a resolution of 300 dpi. Similarly, using CCD sensing devices for an 8-inch wide document as an example, the CCD sensor sets 206a, 206b, and 206c of the CCD sensing devices 202a, 202b, and 202c have 9600, 4800, and 2400 photo-sensing components, respectively. Here, the eight photo sensing components Da1xcx9cDa8, Db1xcx9cDb8, and Dc1xcx9cDc8 are used in the example. The CCD sensing devices 202a, 202b, and 202c, respectively, include CCD shift registers 210a, 210b, and 210c; and the CCD shift registers 210a, 210b, and 210c include 2400, 1200 and 600 CCD components, respectively. The CCD shift register 210a is controlled by phase signals F1a and F2a, while the CCD shift register 210b is controlled by phase signals F1b and F2b, and the CCD shift register 210c is controlled by phase signals F1c and F2c. When shift gates 208a, 208b, and 208c are turned on, the charge signals stored in the CCD components Da1xcx9cDa8, Db1xcx9cDb8, and Dc1xcx9cDc8 can be shifted to the CCD shift registers 210a, 201b, and 210c, respectively.
When the user chooses different scanning modes with different scanning resolutions, the control circuit 204 will choose the outputs of the corresponding CCD sensing devices 202a, 202b, and 202c and send them to capacitor C. Thus, the photo sensor sets 206a, 206b, and 206c are simultaneously exposed to light and store the charge signals in the CCD shift registers 210a, 210b, and 210c while scanning. When choosing the scanning mode of 1200 dpi, the control circuit 204 chooses the output of CCD shift register 210a; or, when choosing the scanning mode of 600 dpi or 300 dpi, the control circuit 204 chooses the output of CCD shift registers 210b and 210c. Since the CCD components of the CCD shift registers 210b and 210c are both far fewer than that of CCD shift register 210a, the time it takes to shift out the stored charges to capacitor C is far less in CCD shift registers 210b or 210c than in CCD shift register 210a. Therefore, using the CCD module in FIG. 2 while scanning at a low resolution will enhance the scanning speed.
Furthermore, using the CCD module 200 in FIG. 2 will confront the following disadvantageous situations. The conventional CCD module uses a chip consisting of three juxtaposed CCD sensing devices with different resolutions. Failure to focus precisely might be caused during exposure to light. The photo sensor sets 206a, 206b, and 206c are parallel with one another and simultaneously receive the light signals from the same optical components. If the optical components are set to focus on the photo sensor set 206a, scanning at a low resolution might result in failure to focus precisely and the scanning quality might be seriously reduced. This makes it necessary to use three different CCD sensing devices belonging to three different chips, thus the required size is very large and the cost is markedly higher.
It is therefore an object of the invention to provide a multi-resolution charge-coupled device (CCD) sensing device, used for scanning at different resolutions. The multi-resolution CCD sensing device along with a photo sensor set and several CCD shift gates and several CCD shift registers achieve economy of size, lower costs, and a higher yield rate. It speeds the scanning at a low resolution, and also greatly reduces the failure to focus, therefore enhancing image scanning quality.
The invention achieves one of the above-identified objects by providing a multi-resolution charge-coupled device (CCD) sensing device, including a first CCD shift register, a second shift gate, and a second CCD shift register. The first CCD shift register has 2M first CCD components, which are Ea[1], Ea[1]xe2x80x2, Ea[2], Ea[2]xe2x80x2, . . . , Ea[M], and Ea[M]xe2x80x2, respectively. Ea[1], Ea[2], . . . , Ea[M] temporarily store M charge signals S[1], S[2], . . . , S[M], respectively. The second shift gate is coupled to the first CCD shift register. The second CCD shift register is coupled to the second shift gate and has 2N second CCD components, which are Eb[1], Eb[1]xe2x80x2, Eb[2], Eb[2]xe2x80x2, . . . , Eb[N], Eb[N]xe2x80x2, respectively. The charge signals stored in the first CCD shift register can be transferred to the second CCD shift register while the second shift gate is turned on. M is equal to L times N, where L is an integer greater than 1, and the charge signals are directly shifted out from the first CCD shift register while transmitting at a first resolution. While transmitting at a second resolution, which is 1/k times the first resolution (where k is a factor of L, L/k=j, k greater than 1), firstly, a variable i is set to 0, i is an integer, and the charge signals stored in the first CCD components Ea[(k*i)+1] to Ea[(k*i)+k] are combined, the charge signals stored in the first CCD components Ea[(k*i+L)+1] to Ea[(k*i+L)+k] are combined, . . . , and the charge signals stored in the first CCD components Ea[(k*i+L*(Nxe2x88x921))+1] to Ea[(k*i+L*(Nxe2x88x921))+k] are combined, and the N set of combined charge signals are stored in the corresponding second CCD components Eb[1], Eb[2], . . . , and Eb[N] respectively. Then, the charge signals, which have been combined in the second CCD components Eb[1], Eb[2], . . . , Eb[N], are shifted out from the second CCD shift register, so as to achieve the first combining and shifting out procedure. Secondly, the value of i is charged from 1 to (jxe2x88x921) in order, wherein each time the value of i is incremented by 1, the combining and shifting out procedure as mentioned above repeat once each time, until all of the charge signals stored in the first CCD shift register are output.
Other objectives, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.